Jeremy Himsel

The Technodyne cars ran GT-25's, o-ringed higher compression head, wide fire head gasket's, APE chips/mass-air, 550CC injectors, stock head studs, a pro-flow mass air "optimizer", and 25 to 28 psi all day long with appropriate fuel and a stock short-block. Of the cars I know with this set-up, no one has a failure after 3 years so you can run the boost up if you know what you're doing. Dyno'd 400RWHP.

J Chen

Rage,
What I'm trying to say is that we should aim to maximize
hp for per pound of boost added instead of just cranking
up the boost. Just look at those big hp cars from Rookes
Gemballa, Ruf. Do you see them using mega boost to gain
those hp figures ? Yes, with race gas it's all together a
different story. 28-29 psi is alot of air, can you imagine
the amount of stress that you're putting on the whole engine ?
Lithium, sorry if I sounded sarcastic. But you have to ask
yourself if it's worth spending that kind of money on a
951 engine. You'll probably have only to spend 30-40 %
of the buget to get 600 hp from a 2JZ & that engine is
bomb proof. I once even joke in one of the threads that
it would be great if we could stuff a 2JZ engine in the 951.

rage2

The 911's have a lot more displacement than we do, thus more power and less boost. The pressure of the air is irrelavent in terms of stress on the motor. It's the amount of O2 molecules (air mass), which translates to cylinder pressure, which translates to torque. If you have a very efficient intake tract and get x amount of air at 15psi vs an inefficient intake tract and get the same amount of air at 18psi, the stress level is the same (except of course for hose clamps, etc. that might work its way loose).

You want more power without changing boost pressure? Here's what you can do:

1. Free up intake tract. Theres only so much you can go though, you can't break the laws of thermodynamics.

2. More displacement. The higher the displacement, the more torque/power you'll make at that boost level.

3. More revs. To get more horsepower, just make more of the maximum cylinder pressure power strokes in a minute. It'll do more work, thus more power.

Option 1 is easy. A Map kit with more efficient turbo, larger IC, and charge piping will net you those results. I got huge power gains and ran lower boost when I converted to standalone and MAP sensing with a T04E turbo. I haven't been able to duplicate that jump in hp/psi since that one single mod (other than displacement change, option 2). What was interesting was that my knock threshold was at 12psi, instead of 18psi on the stock AFM. Why? Because cylinder pressures dictate the knock threshold. Sure I got a lot more hp/psi, but I can NOT run the same psi as before, because the same amount of air is going in the motor, which really made the hp/psi figure useless except for neat bragging rights. Kinda like hp/L.

Option 2 and 3 are pricey, and a lot of work, r&d, troubleshooting, etc.

So... turn up the boost and use high octane fuels... it works. It's not a hack, it's maximizing the amount of air going into the motor. I don't see why high boost is such a bad thing.

RajDatta

Jeremy, you really have my thinking there. I bought one of the Technodyne GT30 setups. This is what he was planning on running on his race car before he decided to go with a 996 race car. I have currently limited boost to .9 bar and this baby with its 3.0 is a monster. When I spoke to Chris, he told me to run no more than 1 bar on street gas. Are these people using race gas? He setup the package to run 1.3 bar and was expecting it to make 465rwhp with similar torque. Should I pump up the boost?
The top end is all Milledge with a stage 3 cam, heavy duty springs and lifters. It has all the bells and wistles to rev upto 7200rpm all day long.
Raj

J Chen

With proper injectors & chip mapping why not.
But you have to have min. Ron 98 octane to be
safe. I'm running 18psi with Ron 98 no problems
& that's without ignition retard.

J Chen

Hi Rage,
With your mods now, have you thought about
taking it to the next level by going 16V ?

rage2

You can NOT state an octane and how much boost you can run, because of #1 that I explained. It's cylinder pressures that dictate octane requirement, not boost level. Someone with a different setup (like me) and following your advice would easily blow up .

Right now I'm at 15psi and just under 400whp. That setting works on 38C days, even drag racing with minimal cooldown. On cooler days (5C) I can run 18psi, which is probably in the 430whp range on pump gas (guess).

My next step is cams, minimize torque drop up top and get more HP that way (revs). The way I see it, my turbo characteristics and stock cams don't match, by using a cam that's more geared towards the 3500-6500rpm range, I can maximize my torque area under the curve without any drawbacks.

lithium

Finally a member who knows what he is talking about. Also considering the CR of the motor is already 8.0to1 (nice and low) i think it might like boost if the air fuel ratios are on the safe side (11, 11.5), tunning is key as already mentioned.

lithium

Jeremy Himsel

Raj, Chris is no different then any other "smart" tuner. He leaves a margin of error for a variety of conditions. Chris also comes from a region where 91 octane is the norm at the pumps. The GT 25 cars would run a race gas mix when in the 2 bar range. I'd get your car on the dyno or use a wideband before I started cranking up the boost. I have seen a GT 25 car run 18 psi in the early phoenix summer without issue on 91 octane.

Can you do this? Only tuning and trials will tell. Good luck.

Duke

Actually I think this is great... I do think the 951-community need more people that are willing to "trial and error" and share their experiences.

The Supras aren't really that superior.. A 700 rwhp Supra-engine needs race gas and major overhaul like new bearings etc. once a year to last.

Lithium>> The "low" rev-limit of the 951 is also somewhat limiting the possible HP compared to other engines more willing to rev 7000+ rpm. And another important thing is the 951 head design. The 8 valve head is NOT very resistant to knock. The 16 valve head is much more resistant to knock (and let's not discuss the Supra head because that's one those engine's best part).
Meaning, the ignition must be quite conservative at extreme boost levels/CFM compared to other engines.
So it's a lot more to it than just looking at one engine and say "hey that one can push 30+ psi all day long then it must be alright to do the same to this other engine"..

But I really hope you build a monster boost 951-engine and post a lot of info about it. Because I'm actually a bit bored always reading the same type of things here like the 6# vs 8# hotside

RajDatta

Oh BTW guys, I forgot to add. I had the car dyno tuned by Larry at Cyntex. Larry is one of the co-founders of APE and has since sold teh company. They spent 4 hrs tuning the car from idle, midrange to WOT. They told me that my bottleneck was stock 951 intercooler and I was sucking too much hot air as my airbox is directly behind the intercooler. They told me 400rwhp is pretty much the limit for stock intercooler. They use a mustang dyno and have wideband.
The car does have a lumpy idle due to a higher duration cam.
Raj

porshhhh951

Lith don't be a smartass. I know what I am talkng about. I never said it couldn't be done. I said it would seriously limit the life of your 2.5ltr motor. No one said you can't go for max hp but, the money argument can not be denied. The money and time you are talking about to build a motor to run 30psi all day long is going to be serious. Rage boosts this high sometimes under certain condition's. I get the impression you wish to leave race gas in the car at all times and run this kind of pressure on a daily basis. I don't care what kind of 951 block you have ...you run 28-30psi every ****ing day racing it and it's gonna go boom.

Someone please prove me wrong. Run 30psi all day everyday see how long it go's without needing a rebuild. And no I don't consider gettting 15 thousand miles outta of motor lasting. To each his own....as long as you don't give a crap what the costs are and how long it lastes then do what makes you feel good man. I just want to educate you on the fact that no one. No one run's those boost pressure daily on this board. Rage one of the very few 951er's on this board who has seen 29psi was for short bursts only. It wasent like he was driving around day in day out like that.


Now if you want to run lower boost level's on pump gas and then every once in awhile turn up the boost with race gas. That's a different arguement. The supra community can run them all day long....we can't. I wait for someone to prove me wrong.

Let's get a test car.....run 30psi on a t04e turbo for 15k miles straight sometimes running the car hard and sometimes not...and see how long it lasts.

porshhhh951

I have a question that I am sure someone here knows.

The zebra 951 race car that was 700hp. How many track day's did it last before rebuild's? I don't know what kind of boost pressure they were running but, I am sure it was alot....and I am sure the motor was fully built. I would be very interested to know this and lithium it might be beneficial to you as well. We could really see what the limit's of the stock motor are and how long they would last under such harsh condition's.

lithium

Well, i think my goal would be 500 or so rwhp, not much more. Remember that there are 1100+rwhp supras out there, so i am not even bring the supra argument in here (your the one that keeps talking about them ) , i dont expect a built 951 motor to survive past 700hp. Also, as previosly mentioned boost itself has very little to do with actual reliability, a WELL tuned motor at 28psi is way safer than a poorly tuned or better yet a non-tuned motor at 18psi But of course you know this as well. I am planning on driving aroung with 300 so hp for a while and comes spring time 72+mm turbo